Dr. Chang is studying protamines—short, positively-charged proteins that condense DNA into chromatin and regulate gene expression in sperm nuclei. While eukaryotic cells use histones to package genomes in a way that allows access for transcription and replication, sperm cells must package their genomes more tightly. For this, many animals deploy protamines instead of histones. Despite sharing certain functions with highly conserved histones, protamines have independently arisen in evolution multiple times and are continuing to rapidly evolution. Using Drosophila fruit fly species as a model, Dr. Chang studies how sperm chromatin regulates gene expression and reproductive fitness. Additionally, although protamine expression is typically limited to testes, their misexpression has been observed in many cancers, indicating an opportunity for therapeutic intervention.

Immune cells called macrophages can swallow bacteria and contain them in membrane-bound compartments called phagosomes. From inside the phagosome, some bacteria stimulate immune pathways in the cytosol, but it is unclear how immune signals are transmitted across the membrane from the phagosome into the cytosol. To investigate, Dr. Jastrab [Robert Black Fellow] has developed a macrophage infection model using mutants of the bacterium Staphylococcus aureus that stimulate an immune complex in the cytosol called the inflammasome. He aims to identify the host and microbial pathways that facilitate activation of the inflammasome during infection. Because the activation of cytosolic immune receptors by phagosomal bacteria may be important in protection against colorectal cancer, Dr. Jastrab’s work aims to elucidate pathways that may be manipulated to prevent tumorigenesis and enhance anti-tumor immunity. Dr. Jastrab received his MD, PhD from New York University School of Medicine, New York and his BS from Tufts University, Medford.

Human cells compact their vast genomes into the small confines of the nucleus by wrapping their DNA into a highly complex structure called chromatin. Packaging DNA into chromatin, however, affects all nucleic acid-transacting machines (e.g., transcription factors) that need to access the genomic information stored in the DNA. NuRD is a large multi-subunit protein complex that plays a major role in making chromatin either accessible or inaccessible. Dysregulation of NuRD and aberrant targeting of the complex can result in the emergence of several types of cancers, including breast, liver, lung, blood, and prostate cancers. Dr. Osorio Valeriano’s [Philip O'Bryan Montgomery, Jr., MD, Fellow] work will reveal mechanistic aspects of NuRD-mediated chromatin regulation and pave the way for the development of novel therapeutic approaches that target cancers more effectively. Dr. Osorio Valeriano received his PhD from Philipps University and his MSc and BSc from the National Autonomous University of Mexico.